1. Field of the Invention
The present invention relates, generally, to a stator assembly and, more specifically, to a torque converter including a stator assembly having a single direction anti-rotation device.
2. Description of the Related Art
In automotive applications, engine torque and speed are translated between a prime mover, such as an internal combustion engine, to one or more wheels through the transmission in accordance with the tractive power demand of the vehicle. Hydrokinetic devices, such as torque converters, are often employed between the internal combustion engine and its associated transmission for transferring kinetic energy therebetween.
Torque converters of the type generally known in the related art include impeller assemblies operatively connected for rotation with the torque input from the internal combustion engine, a turbine assembly fluidly connected in driven relationship with the impeller assembly and a stator assembly. These assemblies together form a substantially toroidal flow passage for kinetic fluid in the torque converter. Each assembly includes a plurality of blades or vanes which act to convert mechanical energy to hydrokinetic energy and back to mechanical energy. The stator assembly of conventional torque converters are locked against rotation in one direction but are free to spin about an axis in the direction of rotation of the impeller assembly and turbine assembly. When the stator assembly is locked against rotation, the torque is multiplied by the torque converter.
The rotation of the stator assembly is conventionally accomplished using a one way clutch interposed between the stator blades and a fixed hub. One way clutches known in the related art typically include an inner race, an outer race with a plurality of roller bearings or sprags disposed therebetween. The bearings or sprags are usually retained between the inner and outer races by cages. The outer race spins or "freewheels" on the bearings in one direction relative to the inner race and is locked against rotation in the opposite direction. This locking or braking action is generally accomplished by configuring the inner diameter of the outer race such that it squeezes or constricts the bearings or sprags when movement is urged in the "locked up" direction.
As noted above, the stator assembly is non-rotatably held during the torque multiplication operating phase of the torque converter. This phase generally extends from stall to the approximate coupling point of the torque converter. The "coupling point" is a term used in the related art to describe the point where the torque ratio is near 1.0. At the coupling point, there is no torque multiplication as described above. When there is no torque multiplication, the torque converter becomes a fluid coupling and the stator "freewheels."
During torque multiplication, the fluid forces acting on the stator can be significant. These fluid forces can generate large, radially directed forces acting through the roller bearings or sprags outwardly through the outer race of the one way clutch. Under certain circumstances, these large forces can cause the outer race to crack or otherwise fail.
Thus, there is a need in the art for a stator assembly which smoothly operates during both freewheel and locked up conditions and which can sustain the large forces to which such stator assemblies are subjected during torque multiplication.
In addition, there is a constant effort in the related automotive art to lower costs by reducing weight, eliminating processing and manufacturing steps and otherwise streamlining the manufacturing process. While conventional stator assemblies and torque converter designs have worked well in the related art, there is an ongoing effort to simplify and thereby lower the costs of the manufacturing process for such stator assemblies and their torque converters. Thus, there is a continual need in the art for torque converters and their subcomponents which include less components and which result in cost and weight reduction over the conventional designs employed in the related art.